A seed meter typically has a housing forming a seed-holding supply chamber and an outlet chamber and a feed wheel rotatable in the housing and formed seed seats. A pressure differential is applied across the disk to move seeds in the supply chamber into the seats, from which they are expelled one by one in the outlet chamber. Such a seed meter is usually used as an agricultural seeder for working a fields and for a uniform dispensing of seeds.
Seed meters particularly serve for separating and dispensing seeds and for inserting the previously mechanically separated seeds at a precise position at predetermined spacings inside rows of a field. Seed meters must separate single seeds safely and carefully from a seed supply and dispense then from the separating device at a chronological and length spacing that is as accurate as possible.
The separating may be carried out, for example, mechanically by so-called star feeders, and/or by pneumatic support or in many other ways. All currently used seed meters are based on the fact that individual seeds are separated from the seed supply and dispensed toward the ground at an even spacing, depending on the driving speed. The seed separation is carried out by setting the single seeds in respective large seats or cells during the processing of the seed supply, and subsequently discharging them one at a time. The seats are bores or grooves formed on on a cell carrier at regular intervals. In mechanical devices the seeds are inserted into the cells by gravity, partially with or against the support of centrifugal force. In pneumatic devices pressure changes effect the separation. Cell supports may be cell wheels or a perforated tape. Ejection from the cell is carried out freely by gravity and/or centrifugal force, partially supported by scrapers.
Most wheel-guided pneumatic cell systems have the peculiarity that the seed briefly moves perpendicular to a main movement direction during dispensing in order to separate itself from the cell, which may cause dispensing inaccuracies in the direction and at time intervals. Seeds are separated from a cell by rotation and released, which in turn causes slight inaccuracies in the tangential separating direction, particularly in the case of smaller perforated wheels. In mechanical systems the cell holes are relatively large in comparison to single seeds, in pneumatic systems the cell holes are smaller than the seed diameter, and are mostly formed holes. There are also dosing devices having guide slots (see U.S. Pat. No. 4,896,616)) where the cells, however, do not open themselves up into the free space.
Due to ever rising drive speeds there is also an increased need for seed output and accuracy of seed dispensing. In order to achieve this, the seed intake and separation must be accelerated in the separators, and the output thereof must be enlarged. The problem may be solved, for example, by a quicker seed intake via an air stream that is as large as possible, or an air stream of large cross-section, while keeping the seed dispensing even.
Above-cited U.S. Pat. No. 4,896,616 discloses a single-seed meter is having a driven seed wheel forming the rear wall of a seed container, connected to a suction blower, and having suction seats for the seeds so as to dispense the suctioned seeds along a path leading from the base area of the container toward the top from the seed area through a container opening from the seed container. The seeding wheel is formed by two parts, namely by a wheel body connected to the suction blower, and by a wheel blade covering the wheel body from the seed, and abutting the wheel body. One of the parts is stationary and forms a guide slot extending along the output path. The other rotatable part has follower slots that are distributed across the circumference thereof and that extend across the radial extension area of the guide slot.
A further device for separating seeds is described in DE 34 00 121. The device has a cell wheel rotatable in a housing and equipped with funnel-shaped bores for receiving the seeds. It is guided by an air stream exiting from a nozzle. The cell wheel is equipped with a ring its outer edge that ends approximately flush with the cell wheel and half of which projects into the funnels of the cell wheel. The ring has bores in the funnels with diameters that are smaller than the smallest seed.
A seeder having cell wheels for single-seed deposition is known from DE 410 440. The cells of the cell wheel are connected to each other by ejection grooves such that the seeds are dropped into the furrows at equal spacings from one or more cell rows by the ejector. Wavy separating walls are arranged between the cell rows to ensure a permanent movement of the seeds.
Further dosing and separating devices for seeders are known, for example, from U.S. Pat. No. 3,888,387, from U.S. Pat. No. 6,176,393, and from U.S. Pat. No. 6,634,522.